Lens grinder



Sept 17, 1957 o w CQBURN 2,806,327

LENS GRINDER Filld March 3, 1954 3 Sheets-Shbet 1 INVENTORK O. n! C'OBURN ATTORNEYS Sept 17, 1957 o. w. COBURN LENS GRINDER Filed March 3, 1954 3 Sheets-Sheet 3 INVENT OR (1 W COBURN ATTORNEYS United States Patent LENS GRINDER 'Orin W. Coburn, Muskogee, Okla.

Application March 3, 1954, Serial No. 413,765

1 Claim. (CI. 51-33) This invention relates to an improvement in apparatus for grinding lenses. More specifically, it relates to an apparatus for grinding simple or compound curved lens faces, including spherical surfaces, which may be either convex or concave.

It is an object of this invention to provide a simple, easily-manufactured, inexpensively-constructed optical lens grinding machine capable of grinding either convex or concave lenses by a simple adjustment without reconstruction of the machine.

Other objects of the invention will be apparent to one skilled in the art from the detailed description of the invention and the attached drawings.

In general, this invention comprises a cup-shaped cutting tool mounted on a tool-holding assembly, a work-holding chuck mounted on a tailstock, a fixed working pivot for the tool-holding assembly and means for shifting the point of engagement between the tool and the work from one side of the pivot to the other.

The shifting means include an elongated tailstock which may be positioned at a wide variety of positions along the length of base of the machine by a handwheel and pinion cooperating with an internal rack, and an extension of the base curve slide extending generally longitudinally with respect to the base for moving the rest of the toolholding assembly across the pivot and backward and forward therefrom.

Also important in the present invention is the provision of a horizontal slide mounting the tool holder proper above the rest of the tool-holding assembly for horizontal movement normal to its axis of rotation. This slide is long enough to serve the dual functions of predetermining which side of the tool will be used for a cutting edge as when shifting from convex to concave work and predetermining the efi'ective cylinder curve setting as in shifting from compound curves to spherical surfaces.

The tool-holding assembly used in this invention includes a conventional longitudinally slidable plate in an extended slideway for predetermining the base curve.

The invention will be better understood by reference to the attached drawings illustrating the preferred form of the invention in which:

Figure 1 is a side elevation of a preferred apparatus of this invention assembled and ready for use.

Figure 2 is a plan view of the device illustrated in Figure 1.

Figure 3 is a cross-sectional view of the device illustratcd in Figure 1 showing the relationship of the structural elements.

Figure 3a is a cross-sectional view of the tailstock cylinder.

Figure 4 is a diagrammatic representation of the maj dj t d to grind concave lenses; and

Figure 5 is a diagrammatic representation of the machine adjusted to grind convex lenses.

Referring now to the drawings, in Figure 1, the ma or elements of the preferred construction can be identified'as a base 10, a tailstock assembly 12, and a tool-holding "ice assembly 14. A cup-shaped cutting tool 16 of standard construction is mounted on the tool-holding assembly for rotation by the driving force of electric motor 18 which tops the tool-holding assembly. A workpiece 20 is mounted on the tailstock assembly and held against rotation during grinding.

The tool-holding assembly is mounted on the base by means of a pivot pin 22 which supports the tool-holding assembly in well 24 in the base. A Timkin type bearing assembly, indicated generally at 26, mounts the pin in the well for free and easy rotation, and this is quite important, as the entire assembly is rotated about this pivot by the operator each time a cut is made. I

A base plate 28 is mounted on the pin 26 and carries a longitudinal slideway 30 of considerably greater length than the ordinary base curve slideway of the prior art. Mounted on the base plate slide 30 are a pair of cooperating cylinder curve plates 32 and 34 which are pivotally joined by pin 36. A base plate carried handwheel 38 turns a screw 40 in a nut 42 which is fixed on the bottom of the lower cylinder curve plate 32 for regulating the longitudinal position of the rest of the tool-carrying assembly on the base plate and with respect to the pivot 22. The upper cylinder curve plate 34 carries the lower. nortion of a transverse slide 44. A tool holder shaft tearing block 46 has its bottom formed as the upper porrion of the transverse slide 44. The bearing block 46 carries a handwheel 48 which turns a screw 50 in a nut 52 fixed on the upper cylinder curve plate 34 for shifting the cup-shaped cutting tool and its supporting shaft transversely across the pivot 36.

The electric motor 18 is mounted on the top of the hearing block 46 for driving the tool 16 by means of a conventional belt drive 56 and rotating shaft 58.

The base 10 carries a bearing block 80, a rack 82 and a pinion 84 which serve as a locking unit for holding the pivot 22 and the tool-holding assembly 14 and in the predetermined degree of rotation. A handwheel 86 is provided for turning the pinion and moving one end of the rack in or out of engagement with the top of the pivot 22.

The tailstock assembly 12 includes a base block 60, a sliding cylinder 62, a check 64 for mounting the work and means for adjusting the longitudinal position of the work. This means includes a handwheel 66 having an axle mounted in the base block 60 for rotating a pinion 68 which meshes with rack 70 at the bottom of cylinder 62. This handwheel operated rack and pinion is for shifting the work from one side of the pivot 22 to the other side to predetermine whether the apparatus will cut convex curves or concave curves. A conventional lock 71 is used for locking the cylinder in a position of coarse longitudinal adjustment. A finer adjustment means includes a handwheel 72 carried by the rear of the cylinder 62, a screw 74 rotated by the handwheel and a chuckholding slide 76 having an internally threaded bore 78 which receives the threaded portion of the screw 74. The base block 60 is mounted on the base by means of a transverse slide 61 so that the work may be shifted transversely as required for adjustment to control prism of the grinding machine.

Adjustment scales are provided at the usual places for,

obtaining accurate adjustments. On the base -curve slide, there is provided a concave curve adjustment scale and .a convex curve adjustment scale 92. The cylinder curve adjustment can be determined by a minus scale 94' for concave surfaces and aplu's scale 96 for convex surfaces. The position of the work is, of cour e, determined by the position of the tool and the starting position of the chuck carrying slide 76 is always such thatthe chuck can be moved forward enough to carry the tool to the point where the grind is complete. Scale 100 associated with handwheel. 72 is provided for predeterrnining the 3 amount of cut to be made on each arcuate swing of the tool past the work.

In general, the apparatus of the present invention is operated by setting the tool and the work in such close proximity to one another that manually swinging the toolholding assembly about pivot 22 will carry an edge of the rotating cup-shaped cutting tool into engagement with the face of the work. The work 20 is held stationary. The motor'18 rotates the tool 16 through the driving assembly illustrated best in Figure l and the tool-holding assembly is swung back and forth in a wide are about pivot 22 by an operator holding the handle at handwhecl 38. On each of these arcuate movements, a single thin cut of the proper curvature is made. The work is then moved towards the t'o'o'l a predetermined amount for a second cut. The entire tool-holding assembly is again swung about pivot 22 so that the tool moves completely past the work and into engagement therewith for a cut of a predetermined depth. The position of the work is again moved toward the tool and another cut is made. Additional cuts are taken until the entire surface of the work conforms to the geometrical pattern defined by the swinging, cup-shaped tool.

The operation just described is the basic operation of the machine, regardless of its settings and regardless of whether the machine is grinding convex or concave lenses. To grind concave lenses one must adjust the position of the tool-holding assembly on the slide 28 so that the pivot 36 and the tool 16 are between the tailstock assembly and the pivot 22. (See Fig. 4.) Likewise, the tailstock cylinder 62 must be shifted in the base block 60 to that position which places the work between the pivot 22 and the base 60.

Thus, to grind a concave lens in the present invention, an operator would proceed as follows: The lens blank is first blocked in accordance with the disclosure in Patent No. 2,465,153 dated March 22, 1949, and the block is mounted in a suitable chuck 64. The predetermined base curve is set by rotating handwheel 38 until the indicator reaches the proper point on scale 90. The predetermined cylinder curve adjustment is made by rotating handwheel 51 until the indicator arrives at the desired point on minus scale 94 as precisely determined by the reading of scale 98. Handwheel 48 is rotated in the proper direction to move the tool assembly unit transversely on slide 44 in the direction opposite the arrow in Figure 2. This positions the tool where the outside of the cup will be the cutting edge. Handwheel 72 is rotated in the proper direction to retract chuck block 76 into cylinder 62. Lock 71 is then released and handwheel 66 is rotated in the proper direction to position the work as shown in Figure 4. Motor 54 is then started and the entire toolholding assembly is swung so that the tool goes past the-work in an arcuate path of the proper geometrical configuration. ,Even a relatively unskilled operator can-make the first cut a light one. Handwheel 72 vis then rotated a given number of units on scale 100 to obtain a predetermined second cut and the tool-holding assembly is again manually pivoted as previously described. Other concave lenses can be ground in a similar manner with an appropriate adjustment of cylinder curves and basecurves. I

To grind a convex lens on the same apparatus, an operator would prepare the work in the same way and adjust the same elements in the same sequence, the only difference being as follows: The tool 16 and the pivot 36 must be shifted to a longitudinal position on that side of the pivot 22 opposite the tailstock assembly 12 and the base curve adjustment will be measured on the plus scale 92 instead of the minus scale 90. The cylinder curve adjustment will be read on the plus scale 96 instead of the minus scale 94. Handwheel 48 must be rotated in the proper direction for shifting the tool in the direction of the arrow in Fig. 2 so that the inside edge of the cup will be the abrading surface and the tailstock cylinder 62 must be shifted in the base block 60 to bring the work into proper relationship with the tool in its new position. The apparatus would then be positioned as illustrated in Figure 5.

Thus, it will be seen that by the apparatus of the present invention, convex lenses and concave lenses can be ground one after the other with only the usual sequence of adjustments necessary for shifting from one grinding to another grinding in prior apparatus useful for only one type curve, and that this apparatus is compact, simple, easilymanufactured and inexpensively constructed.

I claim:

A lens grinding machine adapted to cut convex or concave surfaces by minor adjustment thereof comprising a base, a cup-shaped to'ol, having annular cutting edges, :1 tool-holding assembly, a workpiece and a work-holding assembly, said tool-holding assembly comprising a fixed working pivot mounted on said base, a base curve plate permanently mounted on said base by means of said pivot and forming'the lower half of a longitudinal slide, a pair of pivotally connected horizontal upper and lower cylinder curve plates mounted on said base curve plate with said lower cylinder curve plate forming the upper half of said longitudinal slide which interconnects the base curve plate and the cylinder curve plates, said cylinder curve plates being arcuately adjustable about their pivotal connection for predetermining the cylinder curve, said longitudinal slide being of sufficient length to position the pivotal connection between said cylinder plates longitudinally at either side of said fixed pivot, and means for operating said longitudinal slide to predetermine the base curve, the pivot of said cylinder curve plates being on the tool side of the fixed working pivot for convex curves and on the work side of the fixed working pivot for concave curves, a shaft block for carrying said tool, a transverse slide interconnecting said shaft block and the upper of said cylinder curve plates, means for operating said transverse slide for selectively placing the inside and the outside of said annular cutting edges of the tool in cutting position, the inside being used for convex curves and the outside being used for concave curves, a rotatable shaft in said shaft block for carrying said tool and driving means for rotating said shaft and said tool, and said work-holding assembly comprising a base block on said base, an elongated tailstock cylinder slidably mounted in said base block for positioning said work longitudinally at either side of said fixed pivot, means for shifting said cylinder longitudinally in said base block, in operative relationship with the setting of said longitudinal slide, a chuck on said cylinder forcarrying said work and means for shifting said chuck longitudinally with respect to said-cylinder for taking successive cuts.

References Cited in the file of this patent UNITED STATES PATENTS 

